ATL: GORDON - Post-Tropical

[ScottNAtlanta]

Given the nearly complete lack of shear ( despite all the models still showing it) from here to the Gulf and its current organization could see this spin up pretty quick before florida/keys.

Hey Aric, is it possible the global models are having a hard time with this system because how fairly small system it is. Do you think the hurricane models like the HWRF and HMON will have a different solution.

The global models sometimes struggle with small systems. Models that are high res hurricane models will perhaps have a better handle on this when they run. I noticed that the GFS seemed very under done in its initialization.

[Aric Dunn]

HRRR has changed its tune now ingested some new data perhaps.. 16z vs 17z... it develops a circ underneath the MLC ( could already be starting hard to tell)

https://www.tropicaltidbits.com/analysi ... 90217&fh=1

[ScottNAtlanta]

Timing on this will make a whole lot of difference. The is an upper anticyclone forecast to be over the eastern GOM in 72 hours. If the system is a tad slower it could end up under that and not get sheared at all

[Evil Jeremy]

HRRR has changed its tune now ingested some new data perhaps.. 16z vs 17z... it develops a circ underneath the MLC ( could already be starting hard to tell)

https://www.tropicaltidbits.com/analysi ... 90217&fh=1

How reliable has this model been in similar situations before? Is there a reliable track record?

[gatorcane]

Here is why the NHC has South Florida in the red shading now. The shear is dropping pretty quickly over the Straits and Bahamas so the environment is now conducive for development. Let’s face it, the GFS forecast was not correct as it had the shear over South Florida and southern Bahamas for this weekend keeping this wave in check. But looks like the shear swath nudged west over the Gulf instead. Wouldn’t surprise me if this becomes something before reaching South Florida:

[Aric Dunn]

HRRR has changed its tune now ingested some new data perhaps.. 16z vs 17z... it develops a circ underneath the MLC ( could already be starting hard to tell)

https://www.tropicaltidbits.com/analysi ... 90217&fh=1

How reliable has this model been in similar situations before? Is there a reliable track record?

I mean they are mesoscale models and are not exactly tropical models. but the last couple days they have stuck to seeing this develop today and tonight. and are doing better with the current structure than the normal model suite.

[ScottNAtlanta]

Does anyone know at which point they will run hwrf hurricane models on 91L?

[wxman57]

This isn’t far from developing a surface reflection if not there already. I see no storm outflows to the west or south of this now so at least 3k ft or more above the surface we have a circulation in my opinion. If the current trend holds the rest of today this could become TD7 sometime tonight.

Agree, the only impacts in S. Florida will be some rain tomorrow. However, it's likely going to be a 40-45 mph TS when it reaches SE LA. No TS sustained winds in New Orleans or BTR, just rain.

[SoupBone]

This isn’t far from developing a surface reflection if not there already. I see no storm outflows to the west or south of this now so at least 3k ft or more above the surface we have a circulation in my opinion. If the current trend holds the rest of today this could become TD7 sometime tonight.

Agree, the only impacts in S. Florida will be some rain tomorrow. However, it's likely going to be a 40-45 mph TS when it reaches SE LA. No TS sustained winds in New Orleans or BTR, just rain.

What's your reasoning for a TS versus a quick ramp-up into a hurricane?

[tarheelprogrammer]

This isn’t far from developing a surface reflection if not there already. I see no storm outflows to the west or south of this now so at least 3k ft or more above the surface we have a circulation in my opinion. If the current trend holds the rest of today this could become TD7 sometime tonight.

Agree, the only impacts in S. Florida will be some rain tomorrow. However, it's likely going to be a 40-45 mph TS when it reaches SE LA. No TS sustained winds in New Orleans or BTR, just rain.

What keeps it from being more powerful if shear is dropping along its path? Just curious.

[tolakram]

Shear is not dropping in its path, if anything after this brief window of good conditions shear will continue to increase.

[Aric Dunn]

it is fun looking at the sim IR.. the 18z HRRR is running. it says in 1 hour there is going to be a massive explosion of convection..

https://www.tropicaltidbits.com/analysi ... 90218&fh=1

[chaser1]

Does anyone know at which point they will run hwrf hurricane models on 91L?

I'm pretty sure we'll see an hwrf run at 0Z this evening.

[tolakram]

SLIDER 1min view: http://rammb-slider.cira.colostate.edu/?sat=goes-16&sec=mesoscale_02&x=926&y=1098&z=1&im=60&ts=1&st=0&et=0&speed=130&motion=loop&map=1&lat=0&p%5B0%5D=1&opacity%5B0%5D=1&hidden%5B0%5D=0&pause=0&slider=-1&hide_controls=0&mouse_draw=0&s=rammb-slider

COD: http://weather.cod.edu/satrad/exper/?parms=meso-meso2-02-96-1-100-1&checked=map&colorbar=undefined

[tarheelprogrammer]

Shear is not dropping in its path, if anything after this brief window of good conditions shear will continue to increase.

Isn't the shear inducing ULL dropping SW once this enters the EGOM? NHC mentions more favorable conditions in the GOM. I am confused now lol. Must of missed something.

[Siker]

I see this becoming a TC sometime tomorrow afternoon. Convective activity today, while impressive in structure, is not consistent enough to make me believe there’s organization beginning at the surface. A 60mph TS at SELA landfall is what I’m going with, with most of that intensification happening in a 24 hour period before landfall.

[SoupBone]

Shear is not dropping in its path, if anything after this brief window of good conditions shear will continue to increase.

Finally someone is on my side!

Just kidding of course, but I've been mentioning that the shear in the Eastern GoM continues to increase, albeit slowly. Some posters have mentioned that feature will move in tandem with the system, but so far it hasn't really budged. I'm a novice though, so I defer to others that know more.

[Aric Dunn]

Shear is not dropping in its path, if anything after this brief window of good conditions shear will continue to increase.

well, if you consider the fact the shear was not supposed to drop at all until the gulf and watching the progression of the shear over the past few days it has trended towards shifting west and weakening despite the models being persistent about it staying in place. technically the exact opposite has happened from what the models have been saying.. and the opposite if what the NHC has been saying until the 2pm outlook today..
so following this same progression then its logical to assume the shear axis will continue to shift west with it..


you can easily see the shear axis over eastern florida at the start and is now moving off into the gulf.. pretty straight forward.

http://tropic.ssec.wisc.edu/real-time/a ... tjava.html

[SoupBone]

Shear is not dropping in its path, if anything after this brief window of good conditions shear will continue to increase.

well, if you consider the fact the shear was not supposed to drop at all until the gulf and watching the progression of the shear over the past few days it has trended towards shifting west and weakening despite the models being persistent about it staying in place. technically the exact opposite has happened from what the models have been saying.. and the opposite if what the NHC has been saying until the 2pm outlook today..
so following this same progression then its logical to assume the shear axis will continue to shift west with it..


http://tropic.ssec.wisc.edu/real-time/a ... tjava.html

It has definitively shifted west some, but also expanded itself west as well. Look at the shear tendency loop over the last 24 hours or more. I don't disagree, but It has only degraded/shrunk on that eastern edge a little.

[floridasun78]

i think their chance be a ts by south fl that very slimp- but their keeping eye on it miami weather office